My car won't start. I can't figure out why. I think it has spark. The fuel pump is making its customary whirring noise when I turn the key. I pulled out the spark plugs, but they don't look wet or even smell of gasoline. Is there some way to check to see if the fuel-injection brain is working without buying an expensive scan tool?

MICHAEL SHEEHAN

NEW YORK, NY

A quick check to see if the injection system is working at all can be done with-I kid you not-a device called a noid light. It's simply a small incandescent bulb in a socket with pins that plug directly into the wiring harness leading to your fuel injectors. You can buy a set to fit any number of applications for as little as $15. Pop the connector off the injector and plug the noid light in. Crank the engine over. If the noid light flashes, the computer is operational enough to send voltage to the injector. If not, you'll need to diagnose further. Consider this a quick-and-dirty test only-there are still plenty of things that could go wrong to prevent the engine from starting. Yes, you could do this with a voltmeter, but it's a lot easier to see the noid light flashing than it is to try and read the voltmeter scale.

Is the heater temperature control knob on the dash of your 2002-current Mitsubishi Lancer or Outlander really hard to turn? Technical Service Bulletin (TSB) 05-55-003 says a blend-air door link or gear track is preventing the door from moving freely. Mitsubishi has revised the door assembly-and there's a lengthy procedure to deconstruct the underdash area and replace it.

Drop your 2004-05 T-Bird, Explorer, LS, Aviator or Mountaineer into Reverse and get a loud clunk? Or, maybe it just takes a long time for the tranny to actually go into Reverse? Either way, Ford TSB 05-15-4 says you might need to replace the transmission's solenoid body with a new one to cure the problem.

Our 2005 Nissan Altima has a more than noticeable leak after being driven for a period of time. I put the car on jackstands and the clear fluid collects on the passenger side near the firewall. The dealership says it's water from the air-conditioning system. That was my original guess, but it's never leaked like this before. It even leaks when we don't use the a/c.

BEN RITTERBUSH

SANTA MONICA, CA

Condensate water from the a/c evaporator underdash is normally routed out of the car in the location you describe, so I'm sure this is what you're seeing. Why does this happen when the a/c isn't turned on? Your Altima, like most cars, runs the a/c compressor much of the time--even when you don't think it's on. Any of the settings on the HVAC controller that signify that the windshield demisting is operating will run the a/c to dehumidify the air. That includes during cooler weather when you may, in fact, have the heat turned on. Relax. It's normal.

Premature Graying

There is some gray plastic trim on the side of my car and it has become badly faded. The discoloration is very noticeable. I've tried wax and Armor All, but nothing seems to brighten the color. Is there any product to perk this up, or do I have to remove it and paint it?

HARRY TEICHMAN

BATTLE CREEK, MI

There are a couple of products I'm aware of for restoring black trim-but not gray. Either the painted surface of the trim is, as you surmise, faded by the sun, or the paint film has worn through and what you see is the underlying plastic. Bottom line: You'll have to paint these to achieve a consistent color. Good news: You can use a rattle can to do this, and if you mask carefully, you don't need to remove the trim from the vehicle. Choose an automotive paint for plastics, not something intended for rusty lawn furniture. Bad news: Before painting, you'll need to remove all that Armor All or the paint will squirm around the surface and drip off before it sticks. Thoroughly decontaminate the surface with prep solvent or lacquer thinner. Check a small area first if you use lacquer thinner, lest it dissolve the paint or trim. It shouldn't, if all of the surfaces are still in their factory state. If they've been repainted, the new paint may be less durable than the original.

Walk through the parking lot and check out how many cars have clouded-over headlamp lenses, their plastic surface sandblasted and degraded by the sun. Obviously there's not a lot of light illuminating the road in front of these cars at night. Ultimately, these lenses will need to be replaced, but it's possible to extend their life span. You can go to the auto parts store and buy some ultrafine sandpaper in several successively finer grits and a tub of rubbing compound. Or, you can opt for the convenient Headlight Lens Restoration Kit from Permatex (permatex.com). It has everything you need, including rubber gloves to protect your manicure. The simple procedure takes no more than an hour. The kit retails for under 13 bucks; you probably would spend three times that buying the products separately.

Go-Go Logo

The dealer from whom I purchased my 2005 Ford Explorer attached a chromed advertising logo on the rear of my vehicle. I'd like to remove it, but it's attached very firmly with double-sided tape. Is there a way to do this without causing damage to the paint?

JOHN MLINAR

COLORADO CITY, CO

There are several products I've used. Whichever you choose, work somewhere warm, but out of the sun. Goo Gone will eventually soften the tape, but it might take a few hours. Lacquer thinner will work faster, but it evaporates rapidly; you'll need to keep the tape wetted for at least 10 minutes. The best product I've used for this is 3M Woodgrain & Stripe Remover. You'll find it at an auto parts store or paint store that caters to the automotive body shop or detailing business. This aerosol product will soften the tape fast. The factory enamel on your truck shouldn't be affected by any of these solvents, but I would keep these products away from rubber gaskets and plastic bumpers. Once the solvent works, you should be able to peel the logo off by hand. Try helping it along by sliding an old credit card underneath to slice the tape. Clean up the tape residue with more solvent or a 3M Stripe Off Wheel.

But if I were you, I'd just take it down to the dealer and make them take their advertising off my car.

Knock Three Times

My father has a 2003 VW Passat with the W8 engine, and he uses 89 octane fuel instead of the 91 recommended. He says the knock sensor will adjust the engine timing to prevent knocking and engine damage. I contend that even if the driver doesn't hear pinging, that doesn't mean that it's not occurring, and can lead to engine damage. Can this lower-octane fuel damage his engine?

FREDERICK W.

LEONARDTOWN, MD

Your father will not damage his engine running any gasoline he can get in the United States, which might be as low as 87 in some areas. The knock sensors (many engines have more than one because they are bolted to the head, not the block) will sense the rapidly building pressure waves caused by gasoline igniting prematurely inside the combustion chamber. The engine-management computer will retard this spark and prevent this condition. The system is good enough at this to preclude any damage. The downside is that fuel economy will suffer from the retarded timing, making his bargain low-grade fuel less of a bargain.